Cold germinators originate from winter cold areas. The seeds have a thick and hard shell, through which they survive the winter. Only when frosty temperatures prevail, the plant decomposes a substance which suppresses the germination.
You can seed the cold germinators from autumn. Choose a place where the variations in temperature are not too high and where you can control moisture easily. Make sure that there is no frost outside. Otherwise, you cannot sow the seeds.
The refrigerator as substitute
If you are too late or winter lets you down because the temperatures are too mild, you can use the refrigerator as a cold replacement to simulate the winter artificially. Give a little bit absorbent cotton into a seed bowl. Distribute the seeds in the absorbent cotton and cover them with a thin layer of soil. Then slightly moisten, so that the soil and the cotton are wet and pack it into a plastic bag. It depends on the seed type how long they have to be in the refrigerator. That can be 2 weeks up to several months in the refrigerator at 4 degrees or less to break the sprout inhibition. But pay attention. Too low temperatures destroy the seeds. Afterwards take it out of the plastic bag and sow it into a vessel with potting compost. Keep it warm at a minimum temperature of 12 degrees so that the seeds begin to germinate.
A few examples of cold germinators:
Ranunculus, lily, peony, pansy, sage, primrose, poppy, lady’s mantle